Skip to main content

Full text of "Globally significant plants in southeastern Big Horn and southwestern Rosebud counties, Montana"

See other formats


Globally Significant Plants 

in Southeastern Big Horn 

and Southwestern Rosebud 

Counties, Montana 



Prepared for: 
The Bureau of Land Management 



By: 

Drake Barton and Sue Crispin 

Montana Natural Heritage Program 

Natural Resource Information System 

Montana State Library 



February 2003 




MONTANA 



Natural Heritage 
Program 



Globally Significant Plants 

in Southeastern Big Horn 

and Southwestern Rosebud 

Counties, Montana 



Prepared for: 

Bureau of Land Management 

Miles City Field Office 

lllGarryowenRd. Miles City, MT 59301 

Agreement # ESAO 10009 Task # 5 

By: 

Drake Barton and Sue Crispin 

Montana Natural Heritage Program 




MONTANA 



Natural Heritage 
Prc^jram 



_ ate lllIV Natural Resoiuce 



xl 



© 2003 Montana Natural Heritage Program 

P.O. Box 201800 1515 East Sixth Ave Helena, MT 59620-1800 406-444-3009 



This document should be cited as follows: 

Barton, D. and S. Crispin. 2003. Globally Significant Plants in Southeastern Big Horn and Southwestern 
Rosebud Counties, Montana. Montana Natural Heritage Program, Helena. 27 pp. plus appendices. 

i 



Acknowledgements 



Many thanks to all the individuals who contributed 
to this project. A special thanks to Louise de 
Montigny, Bureau of Land Management, Miles 
City Field Office, for providing logistical support, 
and to Kent Undlin, Dawn Doran and Jeff Gustad 
from the Field Office for their accompaniment in 
the field. Thanks to Amy Taylor who conducted 
fieldwork in 2001. Thanks to Ron Hartman for use 
of the Rocky Mountain Herbarium in Laramie, 



Wyoming, and Dave Dyer for access to the 
University of Montana Herbarium in Missoula, 
Montana for specimen identification. Thanks also 
to Spring Creek Coal for access to known 
locations of Sensitive plants. Another special 
thanks to all the landowners who provided access 
to conduct surveys, much needed directions and 
ice tea after a hot field day. 



m 



Executive Summary 



In 2001 and 2002, botanists for the Montana 
Natural Heritage Program (MTNHP) conducted 
field surveys to locate Astragalus barrii (Barr's 
milkvetch) and Physaria didymocarpa var. 
lanata (woolly twinpod) in southeastern Big Horn 
County and southwestern Rosebud County. Both 
of these species are regional endemics, their 
overall range being restricted to portions of adja- 
cent Montana, Wyoming and South Dakota. A. 
barrii is ranked G3 S2S3 (vulnerable at both global 
and state levels) by the Natural Heritage Network 
(Heidel 2001) and is recognized as a Watch 
Species by the BLM Montana Office. P. 
didymocarpa var. lanata is ranked G5T2 SI 
(indicating the variety is vulnerable at both global 
and state levels) by the Natural Heritage Network 
and has not yet been designated as a Sensitive or 
Watch Species by the BLM Montana Office. 

Previous to this study, both A. barrii and P. 
didymocarpa var. lanata were known to occur 
within the area but had not been systematically 
inventoried. P. didymocarpa var. lanata was 
known in Montana from only one location in Big 
Horn County and had been documented from 14 
occurrences in north-central Wyoming. A. barrii 
had previously been documented from 33 locations 
in southeastern Montana, only two of those in 
southeastern Big Horn and southwestern Rosebud 
counties. 

We identified potential habitat for Astragalus 
barrii and Physaria didymocarpa var. lanata 
prior to beginning fieldwork, using USGS topo- 



graphic maps, soil data (Soil Survey 1996) and 
information in the MTNHP databases. Surveys 
were conducted mainly on larger blocks of public 
land where appropriate habitat was identified, and 
included a total of 25 survey routes. 

These surveys resulted in discovery of four new 
occurrences of P. didymocarpa var. lanata and 
three new occurrences of A. barrii. In addition, 
two new locations were found for another globally 
significant Species of Concern, Lomatium nuttallii 
(Nuttall's desert-parsley). This species is a regional 
endemic, presently ranked G3 SI, and was previ- 
ously known in Montana from one 1980 collection 
in Big Horn County. This species is designated as 
a Watch Species by the BLM in Montana (BLM 
1996). 

These surveys generated significant new 
information on the distribution and habitat of 
globally significant plant species in this area, 
particularly for P. didymocarpa var. lanata and L. 
nuttallii, both of which had only one known 
occurrence in Montana prior to 2001. The fact 
that our surveys were often unsuccessful in areas 
of apparently suitable habitat reinforces that these 
species are uncommon to rare, and do not occur 
predictably and regularly in apparently suitable 
habitat. However, given the relatively small 
proportion of potential habitat that we surveyed, 
additional populations likely exist for all three 
species in unsurveyed areas of suitable habitat 
scattered throughout the region. 



IV 



Table of Contents 

Acknowledgements iii 

Executive Summary iv 

Table of Contents v 

Introduction 1 

Study Area 1 

Methods 2 

Results 3 

Astragalus barrii (Bsin'smi]kYcich) 4 

Physaria didymocarpa var. lanata (woolly twinpod) 10 

Lomatium nuttallii (Nuttall's desert-parsley) 17 

Discussion and Conclusions 23 

References 26 

Appendices 

Appendix 1. Global /State Rank Definitions 
Appendix 2. Maps ofthe Search Routes 

List of Figures 

Figure 1. The five occurrence records for A. /?arn7 in the study area 6 

Figure 2. A. &arn7 close-up 8 

Figure 3. A. fearra plant habit 8 

Figure 4. A. /?arn7 habitat 9 

Figures. A. /?arn7 habitat 9 

Figure 6. The five occurrence records for P. didymocarpa var. lanata in the study area 12 

Figure?. P. didymocarpa YSivJanataFnxiiingiplsinihabiiai 15 

Figure8. P didymocarpa ysly. /a^za^a plant habitat 15 

Figure 9. P didymocarpa yslv. /a^za^a plant with fruits 16 

Figure 10. P. didymocarpa ysly. didymocarpa iplsini in flow tv 16 

Figure 11. The three occurrence records for L. fzz/to//// in the study area 19 

Figure 12. L. nuttallii growth form 21 

Figure 13. L. nuttallii habitat 21 

Figure 14. L. nw to//// close-up showing leaf characteristics 22 

Figure 15. L. nwto//// close-up showing fruit characteristics 22 

List of Tables 

Table 1 . Element Occurrence records for A. barrii in the project study area 7 

Table 2. Element Occurrence records for P didymocarpa var. lanata in the study area 13 

Table 3 . Element Occurrence records for L. nuttallii in the project study area 20 

v 



Introduction 



In 2001 and 2002, botanists from the Montana 
Natural Heritage Program (MTNHP) conducted 
field surveys for the Bureau of Land Management 
(BLM), Miles City Field Office to locate and 
collect additional data on globally significant plant 
species in southeastern Big Horn County and 
southwestern Rosebud County. The purpose of 
this study was to identify additional populations or 
potential habitat, and in the process develop a 
better understanding of the habitat characteristics 
of these species. The information gathered would 
also be helpful in identifying factors that could 
affect the long-term viability of these taxa in the 
area and inform effective management. The 
survey focused on lands administered by the 
Bureau of Land Management, but also included 
state land and occasionally private land when the 
landowner granted permission. 

The primary survey targets were Astragalus 
barrii (Barr's milkvetch) and Physaria 
didymocarpa var. lanata (woolly twinpod), both 
Montana Species of Concern and regional 
endemics, their overall range being restricted 
primarily to adjacent Montana, Wyoming and South 
Dakota. Barr's milkvetch is ranked G3 S2S3 
(vulnerable at both global and state levels) by the 
Natural Heritage Network (Heidel 2001) and is 
recognized as a Watch Species by the BLM 
Montana Office (BLM 1996). Woolly twinpod is 
ranked G5T2 SI, indicating that while the species 
is globally common, this variety is globally rare/ 
restricted and is extremely rare in Montana (Heidel 
2001). Woolly twinpod has not yet been desig- 
nated as a Sensitive or Watch Species by the BLM 
Montana Office. 

Both Barr's milkvetch and woolly twinpod were 
previously documented within the study area, but 
had not been systematically inventoried. Prior to 
this survey, woolly twinpod was known in Montana 
from only one location in Big Horn County. Outside 
of Montana the Wyoming Natural Diversity 
Database has documented an additional 14 occur- 
rences in northcentral Wyoming. Barr's milkvetch 
occurs in South Dakota and Wyoming, and had 



previously been documented from 33 locations in 
southeastern Montana, two of which were located 
within the study area. 

Other Species of Concern documented from this 
area were also sought, though not as vigorously in 
the course of our surveys. Among them was 
Lomatium nuttallii (Nuttall's desert-parsley), 
ranked G3 S 1 and previously known in Montana 
from one 1980 collection in Big Horn County. 
Nuttall's desert-parsley is a regional endemic and 
is designated a Watch Species by BLM in 
Montana (BLM 1996) 

Study Area 

The study area is in southeastern Big Horn County 
and southwestern Rosebud County, Montana, and 
is bounded on the west by the Crow Reservation, 
on the north by the Cheyenne Reservation, on the 
east by the Custer National Forest and by the 
Wyoming border to the south (Figures 1, 6, 11). 
The Tongue River and its drainages comprise the 
core of the study area. 

Tracts of public land managed by the BLM and the 
State of Montana are interspersed among large 
areas of private land, with livestock grazing as the 
dominant land use. Within the survey area, coal 
mining operations are currently localized in south- 
eastern part of Big Horn County. 

Geologically, exposures of the Tertiary Fort Union 
Formation are found throughout the area. This 
formation consists of alternating layers of shale, 
clay siltstone and sandstone, and contains many 
clinkers (also known as red scoria: baked sand- 
stone and shale) and coal beds. The upper part of 
the Fort Union Formation is the Tongue River 
Member, which is the most productive coal-bearing 
geologic section in Montana (Soil Survey 1996). 

Sandy soils generally occur in the higher portions 
of the landscape, associated with a more weather- 
ing resistant caprock; also occurring to a minor 
extent in elevated positions are thermally altered 



shales and mudstones (forming clinker and scoria). 
Soils of mid- to lower-slopes are characteristically 
loams (mostly silt loams), whereas those of the 
toeslopes, terraces and bottoms are silty, often with 
a high percentage of clay. 

Vegetation in this area is characterized by 
ponderosa pine woodland, grassland, sagebrush 
steppe, and barren land on calcareous substrate. 
Ponderosa pine (Pinus ponderosa) and Rocky 
Mountain juniper (Juniperus scopulorum) are the 
only trees present in the uplands, due to the limited 
rainfall conditions. Canopy cover of trees seldom 
exceeds 50% and generally ranges from 10 to 
35%. Hardwood forests are extremely limited, 
with narrow riparian stringers dominated by box 
elder {Acer negundo); wooded riparian areas may 
contain plains cottonwood (Populus deltoides) 
(Carlson and Cooper 2003). 

By far the greatest portion of the landscape tends 
toward dominance by Wyoming big sagebrush 
{Artemisia tridentata ssp. wyomingensis), the 
only exception being restricted habitats such as 
riparian bottoms, ridgeline outcrops. The fact that 
extensive grasslands can be found over slopes and 
flats is attributable to past burning of the range, 
either as a "control" measure or from wildfire. The 
only other shrub of any consequence is black 
greasewood {Sarcobatus vermiculatus), which is 
restricted to alkaline or salt-affected bottomlands 
and also rarely occurs on sideslopes where appro- 
priate soil conditions exist. Small patches of 
Nuttall's saltbush {Atriplex gardneri) were found 
on highly erosive clay outcrops; Dominant associ- 
ates are few and inconsistent. Rhus trilobata / 
Pseudoroegneria spicata was also noted as 
fragmentary occurrences on eroding slope shoul- 
ders of sandy knolls and escarpments. Prairie 
junegrass {Koeleria macrantha) canopy cover is 
higher than would be expected and has probably 
increased as a result of intensive grazing pressure 
on preferred species (Carlson and Cooper 2003). 

Common grassland associations include 
Pascopyrum smithii {Elymus smithii or Agropy- 
ron smithii) n Poa secunda, which occurs on 
fine-textured soils from stream terraces, with soils 
so heavy that drying cracks are wider than an inch; 
it also is found on all but the most xeric of upland 



sites (such as south-facing slopes shoulders, and 
even here it may occur as a depauperate commu- 
nity). Calamovilfa longifolia n Carex inops ssp. 
heliophila occurs as small patches or linear 
extensions on north- or east-facing slopes wtih fine 
sandy soils. Warmer slopes with comparably sandy 
soils have a dominant component of bluebunch 
wheatgrass {Pseudoroegneria spicata or Agro- 
pyron spicatum), or Western wheatgrass 
{Pascopyrum smithii or Agropyron smithii), a 
common grassland community across the Northern 
Great Plains. In this area it usually occurs on 
loamy soils on the upper third of slopes with warm 
aspects, typically associated with sagebrush sites 
that had burned in the recent past (Carlson and 
Cooper 2003). 

Methods 

Prior to beginning fieldwork, we identified potential 
habitat for Astragalus barrii and Physaria 
didymocarpa var. lanata using USGS 
topographic maps, soil data (Soil Survey 1996) and 
information in the MTNHP databases. 

For each species, we developed a search image 
for potential habitat, based on existing information: 

A. barrii: Ridge tops, buttes, outcrops, 

badlands and slopes with sandy 
clay loam soils or calcareous 
substrates; vegetation 
associations of sagebrush- 
grassland, ponderosa pine and 
Rocky Mountain juniper, or 
cushion communities; typically 
sparsely vegetated areas. 

P. didymocarpa var. lanata: Slopes and 
road cuts with red scoria 
(clinker) and clay- shale 
substrates; also calcareous 
substrates and gravelly, unstable 
slopes; emphasis on south-facing 
slopes; sparsely vegetated areas 
in sagebrush-grassland, mixed- 
shrub, and ponderosa pine 
communities; near 3800 feet 
elevation and above. 



While we did not specifically target other Species 
of Concern, they were opportunistically 
documented during the course of surveys. 

Due to annual temperature and moisture 
differences, the optimal survey period for Barr's 
milkvetch and woolly twinpod varies, but is 
normally late May and early June, when both 
species are flowering. Surveys in 2001 were 
delayed, and were conducted between June 18-27. 
In 2002, surveys were conducted from June 5-14, 
during the flowering period for both taxa that year. 

We began survey work by visiting well- 
documented locations to verify that reproductive or 
vegetative structures were present for positive 
identification of both taxa. For woolly twinpod, the 
most diagnostic characteristic is the long, tangled, 
spreading hairs on the leaves. Although leaf 
pubescence is sufficient for identification (Fertig 
2000), fruit characters are also helpful. For Barr's 
milkvetch, flowers or their remnants are necessary 
to distinguish it from co-occurring Astragalus 
species that have compound leaves with three 
leaflets and a cushion-forming habit (Heidel & 
Marriott 1996). Once we confirmed that diagnostic 
characteristics could still be observed in the field, 
surveys were expanded to areas of potential 
habitat. 

Field surveys conducted in 2001 identified one new 
location for both Barr's milkvetch and several new 
locations for woolly twinpod. In addition, several 
other areas were identified as having good 
potential habitat for one or both of these species. 
These potential habitat areas formed the primary 
focus of surveys in 2002. 

Overall, MTNHP botanists walked approximately 
25 survey routes in different areas identified as 
potential habitat. Survey routes are indicated on 
the 1:24,000 USGS Quad maps in Appendix 2 by 
solid red lines. Priority was given to potential 
habitats on the largest tracts of BLM-administered 
land in the study area, but surveys were also 



conducted on smaller BLM blokes, on state land 
and, where permission was granted, on private 
land. Access permissions from landowners were 
documented wherever private land was entered 
for access or surveys. 

For each population of A. barrii, P. didymocarpa 
var. lanata, or L. nuttallii visited in the field, we 
completed an MTNHP Plant Species of Concern 
Survey form, including documentation of 
Ecological Rangeland Sites (Natural Resources 
Conservation Service 2000). Global Positioning 
System (GPS) coordinates were taken for new 
locations of the target species. Where appropriate, 
photographs were taken. Voucher specimens were 
collected and verified at the Rocky Mountain 
Herbarium in Laramie, Wyoming, and at the 
Herbarium at the University of Montana 
(MONTU). 

All data collected on Species of Concern were 
entered into the MTNHP databases and 
corresponding spatial coverages. 

Results 

Our surveys identified three new locations for 
Barr's milkvetch, four new locations for woolly 
twinpod, and two new locations for Nuttall's 
desert-parsley. Of the 25 routes surveyed, we 
found new occurrences of globally significant plant 
species along nine of these routes. 

The following speciesi descriptions summarize 
information available on each species. All 
occurrences in the study area are listed in Tables 
1-3 and mapped in Figures 1, 6, and 11. The 
identifying numbers in both the Figures and Tables 
correspond to occurrence numbers assigned in the 
MTNHP data system. The species descriptions 
also summarize broader distributional patterns, 
identifying characteristics, and habitat, including 
NRCS Rangeland Ecological Sites on which they 
occur. 



Barr'sMilkvetch 

Astragalus barrii Bameby 

Occurrence in the Study Area 

Figure 1 shows the mapped locations of all Barr's milkvetch occurrences that have been documented in 
the study area, and Table 1 lists each occurrence. Three new occurrences of Barr's milkvetch were 
documented in this study (bolded in Table 1), bringing the total for the study area to five. One new 
population is small, consisting of only four clumps, however the other two are considerably larger, one 
with more than 200 plants and the other with over 500 individual plants. Population sizes in the state vary 
widely, ranging from less than 10 to thousands of individuals. 

Identification 

Barr's milkvetch forms dense mats (cushions) that rarely exceed 25.9 cm in height. Prostrate woody 
stems give rise to numerous leaves, each made up of narrowly elliptic leaflets that are 1-4 cm long. Both 
the stems and leaves of A. barrii are densely covered with short, white hairs. Iridescent bluish-purple to 
pinkish-purple flowers arise on short stalks (7-16 mm) throughout the mats on narrow, open, (1) 2-4 
flowered inflorescences. The petals are 7-17 mm long. The calyx is 3-5 mm long and densely covered 
with long, white hairs. The sparsely white-hairy pod is narrowly elliptical, 4-8 mm long, and 1-2 mm wide. 
In Montana, this species blooms from late April to mid- June and later forms narrow, egg-shaped, one- to 
few-seeded pods. A. barrii may remain in a vegetative condition under stressful conditions. 

Barr's milkvetch is distinguished by its small, iridescent, bluish-purple to bluish-pink, early-blooming 
flowers. Petal color may fade, sometimes to yellowish- white, as flowers dry (Taylor 2001). Flowers are 
necessary to distinguish A. barrii from four other mat-forming, 3-leafleted Astragalus species that 
overlap geographically with it in Montana: A. aretioides (Sweetwater milkvetch), A. sericoleucus (silky 
milkvetch), A. gilviflorus (plains milkvetch) and A. hyalinus (summer milkvetch). 

A. aretioides and A. sericoleucus have flowers that are typically one-half the size of A. barrii, and tend to 
grow in denser mats. Both species are known from Big Horn County, but were not encountered during the 
survey. 

A. gilviflorus and A. hyalinus typically have larger, cream to whitish flowers. They also differ from A. 
barrii by having a longer calyx tube (6-16 mm) and absent or shorter (<3.5 mm) peduncles (A. barrii: calyx 
length 2.8-5 mm, peduncle length 7-24 mm). Known in Montana from the Pryor Mountains and from the 
Ashland District of the Custer National Forest, A. hyalinus is similar in growth habit to A. barrii and is found 
in similar habitats. 

The only similar Astragalus species observed during this survey was A. gilviflorus, which is very 
abundant in the study area and occurs in the same habitat and locations as A. barrii. The majority of A. 
gilviflorus plants were at the end of their blooming period. Vegetatively, A. gilviflorus appears more 
robust, with longer leaf petioles and larger leaflets than A. barrii. The flowers, when present, are 
distinctly larger than those of A. barrii. 

Distribution 

Barr's milkvetch is endemic to southwestern South Dakota, northeastern Wyoming and southeastern 
Montana. A total of 35 occurrences have been documented in Montana: three in Big Horn County 
(includes one new from this survey), 13 in Rosebud County (includes two new from this survey), 18 in 
Powder River County, and one in Carter County. 



Habitat 

Habitat data for the three new occurrences of Barr's milkvetch in the study area are consistent with 
other information for the species (see Table 1). It occurs on heavy clay ("gumbo") knobs, badlands, 
buttes and barren hilltops, often on calcareous soft shale and siltstone substrates (Heidel & Marriott 
1996). The calcareous clay soils on which A. barrii occurs are likely to be low in organic matter, as these 
locations are sparsely vegetated (Schassberger 1990). The elevation range is 3,140n4,160 feet. 

Barr's milkvetch habitats sometimes have scattered ponderosa pine or Rocky Mountain juniper, but often 
there is only a sparse shrub cover of big sagebrush and/or shadscale (Atriplex confertifolia). Generally, 
in southeastern Montana, Barr's milkvetch habitat is dominated by Western wheatgrass (Pascopyrum 
smithii or Agropyron smithii) thickspike wheatgrass (Elymus lanceolatus or Agropyron 
dasystachyum), green needlegrass (Nassella viridula or Stipa viridula), little bluestem (Schizachyrium 
scoparium or Andropogon scoparius), bluebunch wheatgrass {Pseudoroegneria spicata or Agropyron 
spicatum), prairie junegrass {Koeleria macrantha or Koeleria cristata), native legumes, big sagebrush 
(Artemisia tridentata), Nuttall's saltbush (Atriplex gardneri) and winterfat (Krascheninnikovia lanata 
or Ceratoides lanata) (Heidel & Marriott 1996). 

A. barrii grows under harsh edaphic and environmental conditions with limited rainfall and high light 
intensities. This can limit plant establishment and survival due to high soil water evaporation. Barr's 
milkvetch often occurs on barren, eroded microsites and may depend on climate to maintain these sites 
and keep vegetative competition low. At some locations, particularly steep slopes, the soils erode during 
intense rainstorms. Because of its cushion habit and dense foliage, soil is protected from water erosion 
beneath A. barrii plants, resulting in individuals that are frequently perched atop small pedestals of soil 
(Heidel & Marriott 1996). 

Rangeland Ecological Sites 

The three new occurrences of A. barrii were found on the Badlands (BL) Rangeland Ecological Sites, 
characterized by hills and knobs that appear more rounded, and have outcrops of shales as a dominant part 
of the landscape. There is frequently evidence of salts, often occurring around the base of hills and knobs. 
Very few trees occupy these sites, with the exception of an occasional Rocky Mountain juniper. 
Vegetation is sparse, and the species present are often typical of clayey sites, but with a greater 
abundance of shrubs (USDA 2000). 



Astragalus barrii 




Study Area p 



Asijra gatwsh ami 

I I Townshipff^angs 

Seclrap- 
OWNERSHIP 

BUM 

BOR 

USFVyS 

USFS 
US DA 
^H CUE 

DMRC 
DFWP 
Univmily 
St)it4 lniHJlJi?n? 

PtiMrtt 



Figure 1 . The five occurrence records for Astragalus barrii in the study area. There are three occurrences (including one new occurrence from 
this study, 044) in southeastern Big Horn County, and two new occurrences (both new from this study, 043, 045) in southwestern Rosebud County. 

6 



Table 1. Element Occurrence (EO) records for Astragalus barrii Bameby in the project study area. Selected descriptive fields are from the Heritage database, with new 
occurrences highlighted in bold text. 



EO 



Number ^**""^ Survey Site Element Occurrence Data 



General Description 



Major Land Rangeland ^ ^^ . , . ^ Township „ . 
Resource Area Ecolo|cal Site ^"*'*»'>* longitude ^^^^^^ Section TRSNote 



043 Rosebud Whitten Creek 4 major mats/clumps 

(approx. 12 cm wide) on 



HiHs of red shale, sandstone, and Eastern 

badlands. NW-facing knob of badlands, Sedimentary 



Badlands (BL) 451908N 1063519W 006S042E 16 NE4 



knob. Fruiting with some very sparsely vegetated. Associated 



remnant flowers. 



species include Sarcobatus vermiculatus, 
Pinus ponderosUf Juniperm scopuloruntf 
Cryptantha sp., Agropyron spicatum; 
Astragalus gilviflorus common on same 
hills. 



Plains, 58AE 



044 Big Horn South Fork Spring Over 500 clumps in two 

Creek / Squirrel main clusters still in flower. 
Creek 



Deeply eroded, rounded knobs of 
badlands, soft soils of siltly clay. 
Sparsely vegetated with Artemisia 
tridentatOf Pinus ponderosa^ Juniperus 
scopulorum, Phlox hoodii, Astragalus 
bisulcatuSf Agropyron spicatum 



Eastern 
Sedimentary 
Plains, 58AE 



Badlands (BL) 450626N 1065740W 008S039E 



28 



045 Rosebud Whitten Creek 



Over 200 clumps in two 
separate subpopulations, 
many still in full flower. 



Hills of red siltstone sandstone, and 
badlands. NW- and SE-facing slope of 
badlands, very sparsely vegetated. 
Associated species include Rhus 
trilobata Artemisia tridentata, Pinus 
ponderosttf Juniperus scopulorun% Phlox 
hoodiif Agropyron spicatum; Astragalus 
gilviflorus common on same hills. 



Eastern 


Badlands (BL) 452009N 


1063614W 


006S042E 


5 


NE4 


Sedimentary 








8 


NW4 


Plains, 58AE 













003 Big Horn 



Decker 



028 Big Horn Spring Creek 



Common. 



Barren clay soil on ridgetop, with 
Haplopappus acaulis and Eriogonum 
pauciflorum. 



This occurrence contains 7 On fine, sandy-clay loam soil, above a 
subpopulations spread over an sandstone outcrop, and bare, dry fine soil 
area roughly 4 miles E-W by or shale, with Artemisia tridentata, 
1.5 miles N-S. Each Agropyron spicatum, Phlox hoodii, 

subpopulation has from 20 to Astragalus gilviflorus, Oxytropis sericea, 
1000 plants. and Eriogonum sp. 



450102N 1065349W 009S039E 



450702N 1 06550 1 W 008S039E 



25 


NE4 


23 


NW4SE4; 




15SW4; 




16SE4;22 




NE4; 13 




N2;14 




NE4. 



Bolded records indicate new occurrences documented during this survey. 




Figure 2. Astragalus barrii close-up. Whitten Creek, Rosebud County. 




-^i< 

" ,-;,>-^' 




<'»;*>, 






.''/:;' ' "o^^s;^'^^ 



1^^ : ■*^- 






-1 



"A 



+- 



<■ 



7^^ 

Figure 3. Astragalus barrii plant habit. Whitten Creek, Rosebud County. 

8 



^n^^ 



t:- - '■ 



■J 



\- 



■"v'«i; 






f ..-i^'^ 




J\ 



s;^- 




Figure 4. Astragalus barrii habitat. Whitten Creek, Rosebud County. 




Figure 5. Astragalus barrii habitat. Squirrel Creek, Big Horn County. 

9 



Woolly Twinpod 

Physaria didymocarpa var. lanataA. Nels. 

Occurrence in the Study Area 

Figure 6 shows the mapped locations of all woolly twinpod occurrences that have been documented in the 
study area, and Table 2 lists each occurrence. Four new occurrences were documented in this study 
(boldd in Table 2) bringing the total number for the study area to five. Population sizes for all woolly 
twinpod occurrences in the area range from 16 plants to thousands of individuals. 

Identification 

Woolly twinpod is a tufted, multi-stemmed perennial herb covered with long-stalked, tangled, multi- 
branched woolly hairs (giving the entire plant a gray appearance). Basal leaves are entire to coarsely 
dentate and shaggy-margined due to the long-stalked pubescence. Stem leaves are shorter, oblanceolate, 
and 1-2 cm long. The inflorescence consists of a congested cluster of yellow, 4-petaled flowers 8-12 mm 
long. Mature fruits appear as two inflated, balloon-like pods with shaggy pubescence. The replum of the 
mature fruit is narrowly lance-shaped to oblanceolate with 2 stubby funiculi (stalks connecting ovule to 
placenta) per face. Flowers are borne from May-June, with fruits produced as late as September (Fertig 
2000). 

Many similar Physaria species exist in Montana, and a microscope or hand lens, technical keys and 
reference to herbarium specimens are recommended for positive identification. P. didymocarpa var. 
lanata is distinguished by leaf pubescence, having long, tangled, spreading hairs, especially evident at leaf 
bases. In contrast, P. didymocarpa var. didymocarpa (common twinpod), has appressed hairs on the 
basal leaves giving them a smooth look (Figure 10), and there are mostly 3-6 ovules/funiculi per locule. P. 
acutifolia (sharp-leaf twinpod) also has leaves with appressed hairs. 

P. brassicoides (double twinpod) is the most similar to woolly twinpod, and grows in eastern Montana on 
clay hills and road cuts. However, double twinpod has appressed leaf hairs and a narrowly linear fruit 
partition, whereas woolly twinpod has shaggy hairs and narrowly lanceolate to oblanceolate partitions 
(Dorn 1992; Fertig 2000). 

Distribution 

Woolly twinpod is a regional endemic, restricted to north-central Wyoming and southeastern Montana. 
Five occurrences have been documented in Montana n two in Big Horn County (includes one new from 
this survey) and three in Rosebud County (all new from this survey). 

Habitat 

Habitat information for woolly twinpod in the study area has been greatly improved with the discovery of 
four more occurrences. Habitat summaries are provided in Table 2. It occurs on sandstone outcrops, 
redbed clay (clinker or scoria)-shale slopes, calcareous substrates, and road cuts, where it occupies open, 
shrub-dominated slopes, sometimes with a sparse cover of ponderosa pine and Rocky Mountain juniper. 
Common associates include ponderosa pine. Rocky Mountain juniper, fragrant sumac {Rhus trilobata), 
big sagebrush, bluebunch wheatgrass, and needle-and-thread grass (Hesperostipa comata or Stipa 
comata). Elevation varies from 3300 to 4100 feet. 

Rangeland Ecological Sites 

The four new occurrences of P. didymocarpa var. lanata were found on Coarse Clay (CC), Badlands 
(BL) and Thin Breaks (TB) Rangeland Ecological Sites. Coarse Clay (CC) Rangeland Ecological Sites 
occur on undulating to rolling uplands, fans, foot slopes and low ridges. Coarse Clay sites are normally 

10 



located on unstable landscapes of slumping shales, commonly with hummocky or dune-like topography. 
These sites have soils with less than 10 inches to hard bedrock. 

Badlands (BL) Rangeland Ecological Sites are characterized by hills and knobs that appear more 
rounded, and have outcrops of shales as a dominant part of the landscape. There is frequently evidence 
of salts, often occurring around the base of hills and knobs. Very few trees occupy these sites, with the 
exception of an occasional Rocky Mountain juniper. Vegetation is sparse, and the species present are 
often typical of clayey sites, but with a greater abundance of shrubs. 

Thin Breaks (TB) Rangeland Ecological Sites are characterized by a landscape that has steep to very 
steep, angular and rough topography, with the tops of these sites appearing somewhat level. Outcrops of 
sandstone, siltstone or other hard rock dominate parts of the site. There are numerous ledges where an 
occasional tree occurs. The majority of vegetation is generally typical of sandy or silty sites, but with 
more shrubs (USDA 2000). 



11 



Physaria didymocarpa van lanata 



ffi^Ei 



iO$.^E 




Figure 2. The five occurrence records for Physaria didymocarpa var. lanata in the study area. There are two occurrences (including one new 
occurrence from this study, 002) in southeastern Big Horn County, and three new occurrences (all new from this study, 003-005) in southwestern 
Rosebud County. 1 2 



Table 2. Element Occurrence (EO) records for Physaria didymocarpa var. lanata A, Nets, in the project study area. Selected descriptive fields are from the Heritage database, 
with new occurrences highlighted in bold text. 



EO 

Number 



County Survey Site 



Element Occurrence Data 



General Description 



Major Land R«"geland ^^^,„^^ l^or^HnAt ^o^-nship ^^^^ ^^^^^^ 

Resource Area Ecological Site * and Range 



002 Big Horn Tidwell Draw 



Over 100 individuals covering 
entire south-facing exposure; 
95% fruiting; <5% vegetative. 
5 or 6 large individuals (>20 
cm wide with fruits). 



Steep, sandy, south-facing slope 
above draw with sandstone outcrops 
and fragments; fairly productive 
slope - high grass cover. Shrubs and 
grass community with an occasional 
Juniperus scopulorum or Pinus 
ponderosa. Grasses dominate: Stipa 
comata, Agropyron spicatunu Bromus 
japonicus. Shrubs and forbs: Rhus 
trilobatOf Artemisia tridentaia^ 
Ceratoides lanata^ Astragalus 
gilviflorus. Yucca glauca, Opuntia 
polyacantha. 



Eastern 


Thin Breaks 


450330N 


1061909W 


009S044E 


15 


NW4; 10 


Sedimentary 


(TB) 










SE4SW4 


Plains, 58AE 















003 Rosebud Zook Creek Approximately 50 individuals; Southwest-facing slope of redbed 

20% fruiting, 80% vegetative shale and sand east of creek. Red 
(basal rosettes only). Doesn't shale and sand slope below sandstone 
occur in areas of slope that are outcrop. Moderately steep slope, 
significantly composed of red Open slope of Pinus ponderosa and 
shale. Juniperus scopulorum; bunch grasses 

and shrubs also common. Associated 
species include trees: Pinus 
ponderosUf Juniperus scopulorum; 
shrubs: Yucca glauca^ Rhus trilobata^ 
Atriplex confertifolia; grasses: 
Agropyron spicatum^ Stipa comata^ 
Bouteloua curtipendula; forbs: Gaura 
coccineOf Sphaeralcea coccinea^ 
Psoralea sp. 



Eastern 
Sedimentary 
Plains, 58AE 



Coarse Clay 
(CC) 



452032N 1063325W 006S042E 



NW4SW4; 3 
NE41WV4 



13 



EO 
Number ^"'"'^ 



Survey Site 



Element Occurrence Data 



General Description 



Major Land 
Resource Area 



Rangeland 
Ecological Site 



Latitude Longitude 



Township 
and Range 



Section TRS Note 



004 Rosebud Bull Creek Fairly abundant; 16 

individuals in one area, 
occupying approx. 20 square 
feet. 



Sandy, rocky, southwest-facing slope 
of roadcut, clinker-shale mix, 
sparsely vegetated. Southwest-facing 
slope adjacent to 2-track road. Loose, 
sandy shale. Dominated by grasses; 
interspersed with Rhus ttilobata and 
Artemisia cana. Associated species 
include Agropyron spicatum, 
Artemisia cana, Artemisia frigida, 
Rhus trilobatay and Eriogonum sp. 



Eastern 
Sedimentary 
Plains, 58AE 



Coarse Clay 
(CO 



452025N 1064042W 006S041E 



S2SW4 



005 Rosebud Canyon Creek 



19 individuals occuping 
approx. 100 square yards. 
95% fruiting, 5% vegetative. 



Generally barren sandstone 
outcrops; calcium carbonate present; 
south-facing slope. Juniperus 
scopulorum on the slope above. 
Slopes are shrub dominated with 
Chrysothamnus nauseosus, Artemisia 
canUi Rhus trilobata. Agropyron 
spicatum also present. 



Eastern 
Sedimentary 
Plains, 58AE 



Badlands (BL) 451508N 1064256W 007S041E 



NW4NE4 



001 Big Horn Spring Creek 



2001; locally abundant; 90% 
flowering, 10% basal rosette 
only. Size of occupied area is 
similar to 1993 estimate. 1993: 
flowering mostly in May, but a 
few plants still flowering in 



1993; "scoria" and sometimes shale 
substrate. 2001; steep southwest-facing 
slope of red scoria and shale substrate; 
hills rise from Spring Creek 
bottomland. Characteristic associated 
species include Stipa comata, 
August. Locally abundant, 1 000- Agropyron spicatum, Oryzopsis 
2000 plants. hymenoides, Phlox hoodii. Other 

common species include; Chaenactis 
douglasii, Sphaeralcea coccinea. 



450804N 1 065 533 W 008S039E 



14 N2;22E2 



Bolded records indicate new occurrences documented during this survey. 



14 







Figure 7. Physaria didymocarpa var. lanata; fruiting plant habit. Spring Creek, Big Horn County. 




Figure 8. Physaria didymocarpa var. lanata habitat. Zook Creek, Rosebud County. 

15 




Figure 9. Physaria didymocarpa var. lanata plant with fruits. Tidwell Draw, Big Horn County. 




Figure 10. Physaria didymocarpa var. didymocarpa plant in flower. This variety looks 
similar but appears smoother look and lacks the long hairs of variety lanata. 

16 



Nuttairs desert-parsley 

Lomatium nuttallii (Gray) J.F. Macbr. 

Occurrence in the Study Area 

Figure 11 shows the three mapped locations of Nuttall's desert-parsley documented in the study area, and 
Table 3 lists each occurrence. Of the two newly discovered populations (bold printed in Table 3), one has 
over 300 individual plants, while the other is considerable smaller, with only 30 plants observed. 

Identification 

L. nuttallii is an upright perennial herb that reaches a height of 1-4 dm tall. These plants are glabrous, 
yellow-green in color and have a pleasant, aromatic scent. The basal leaves are once or twice pinnately 
compound or three-parted. The leaf blades are 2-15 cm long with ultimate linear divisions that are 1-2 mm 
wide and some greater than 1 cm long. The leaves arise from a thickened rootstock that is covered with 
old leaf bases. The leaf petioles are expanded and sheathed at the base. Several to many small flowers 
are borne in flat-topped, compound umbels on stout, leafless flower stems that are generally taller than the 
leaves. Involucels of united or separate linear segments subtend the umbellets and often protrude beyond 
the flowers. Flowers have 5 petals and 5 stamens attached above a single, two-chambered pistil with two 
styles. The mature fruits are flattened and narrowly oval-shaped with marginal wings and low ribs on the 
flat faces; they are 5-9 mm long and 3-4 mm wide. Fruiting pedicels are mostly 1-2 mm long. Flowering is 
usually in June, with fruits produced by July. 

Mature fruits and the leaf arrangement are distinctive features used to separate this species from similar 
Lomatium species. Key characteristics are its non-lacy leaves, the persistence of the old leaves at the 
base of the plant, lack of hairs, and relatively small fruits. Two similar species of Lomatium occur in 
Montana: L. triternatum (nine-leaf lomatium), which is likely to occur within the study area, is normally 
somewhat hairy and has tritemate leaves, some of which are on the flowering stem; L. ambiguum 
(streambank desert-parsley), a more western species, also has leaves on the flowering stem and lacks 
involucels. Another similar species known from Wyoming but not yet documented in Montana, L. 
graveolens (king desert-parsley) is very similar and is best separated by the larger fruits (10-13 mm), 
longer fruiting pedicels (2-7 mm), and a smell that is notably malodorous. 

Distribution 

Lomatium nuttallii is a regional endemic. It is most abundant in central Wyoming, with at least one 
occurrence in Colorado, and a few occurrences in Nebraska. It was historically reported from South 
Dakota but is thought to be extirpated in that state. In Montana, it is known only from three locations: two 
in Big Horn County (one new from this survey) and one in Rosebud County (new from this survey). 

Habitat 

The two new occurrences of Nuttall's desert-parsley provide additional data on this speciesi habitat in 
Montana. Nuttall's desert-parsley grows on open, rocky slopes of sandstone, siltstone or clayey shale, in 
open pine woodlands. The vegetation is generally sparse, and commonly includes ponderosa pine. Rocky 
Mountain juniper, bluebunch wheatgrass. Western wheatgrass, big sagebrush, and rubber-rabbitbrush 
(Ericameria nauseosa or Chrysothamnus nauseosus). Elevation ranges from 3400 to 7200 feet. 

Rangeland Ecological Sites 

Of the L. nuttallii occurrences, one was found in a Thin Breaks (TB) Rangeland Ecological Site and the 
other in an area that keyed to an Overflow (OV) site. This location is in a very dry creek bottom adjacent 
to an ephemeral stream. The associated vegetation was more abundant and diverse than the surrounding 

17 



uplands. Some of the trees were green ash (Fraxinus pennsylvanica), with Rocky Mountain juniper and 
ponderosa pine also abundant. 

Overflow (OV) Rangeland Ecological Sites are located adjacent to ephemeral streams, with the water 
table not present within 3.5 feet of the soil surface. Vegetation is obviously different from the adjacent 
uplands. Thin Breaks (TB) Rangeland Ecological Sites are characterized by a landscape that has steep to 
very steep, angular and rough topography, with the tops of these sites appearing somewhat level. Out- 
crops of sandstone, siltstone or other hard rock dominate parts of the site. There are numerous ledges 
where an occasional tree occurs. The majority of vegetation is generally typical of sandy or silty sites, but 
with more shrubs (USDA 2000). 



18 



Lomatium nuttallii 




I l^iLes 



a 1.5 3 



6 



9 



12 




Study Area 



Cti£4EE 



Legend 

■^^ hl^ragraplit 

I I TQWl3Mpil^*iafi 

SecUnn 

BLM 
^B BOA ^SuRk:) 

NP£ 

USPS 
^B Othrf USQA 
^B USFIAIS 

SATnJfft 

Tribal 

DFVWP 
^^1 U^ivenrty A InsUliriiGnc- 
^^1 CHj^Mlly 4 Crty 

P\\M\1 Crtek 
^^1 Ptrvabc CDnsmiabGn 



Figure 3. The three occurrence records for Lomatium nuttallii in the study area. There are two occurrences (including one new occurrence 
from this study, 002) in southeastern Big Horn County, and one new occurrence (new from this study, 044) in southwestern Rosebud County. 

19 



Table 3. Element Occurrence (EO) records iorLomatium nuttallii (Gray) J.F.Macbr. in the project study area. Selected descriptive fields are from the Heritage database, 
with new occurrences highlighted in bold text. 



EO 



Number ^**""^ Survey Site Element Occurrence Data 



General Description 



Major Land Rangeland , ... , , .^ , Township „ .- ^«c. i,.t . 

Resource Area Ecological Site ^^^'^"^^ Longitude ^^^j^^^^^ Section TRSNote 



002 Rosebud Tongue River Over 300 individual clusters, Steep, rocky, southwest- and 

in 2 separate groups. In late northeast-facing slope above draw, 
flower and early fruit. siltstone outcrops and rock 

fragments covering the surface* 
Sparce vegetation with a dense 
Juniperus scopulomm and Pinus 
ponderosa cover close by. 
Juniperus scopulomm, Pinus 
ponderosa, Agropyron spicatum^ 
Cryptantha celosioides, Lesquerella 
alplna, and Haplopappus acaulis 
are common associates. 



Eastern 
Sedimentary 
Plains, 58AE 



Thin Breaks 
(TB) 



450935N 1064319W 007S041E 



32 NC 



003 Big Horn Tongue River 



Approximately 30 individuals. Northern aspect of a dry drainage 
In late flower and early fruit, bottom. A wide spot in the channel 
with substantial tree cover. 
Fraxinus pennsylvanica, Juniperus 
scopulorum, Agropyron smithii, 
Sywphoricarpos occidentalism 
Toxicodendron rydhergii. 



Eastern 
Sedimentary 
Plains, 58AE 



Overflow (OV) 451225N 1064424W 008S041E 



SW4 



001 Big Horn Squirrel Creek No information provided. 



First collection in Montana. On Eastern 

shallow, rocky soil of a sandstone Sedimentary 

cliff. Associates moXudit Agropyron Plains, 58AE 
spicatum, Pinus ponderosa and 

Juniperus scopulorum. 



Thin Breaks (TB) 450135N 1065159W 008S040E 20 SW4 



Bolded records indicate new occurrences documented during this survey. 



20 



w^^^^ 








Figure 12. Lomatium nuttallii growth form. Tongue River, Rosebud County. 
Old leaves remain at base of plant. 




Figure 13. Lomatium nuttallii habitat above Tongue River, Rosebud County. 

21 




Figure 14. Lomatium nuttallii close-up showing leaf characteristics. Tongue River, Big Horn County. 





.V 

1 El ^ 




i 



Figure 15. Lomatium nuttallii close-up showing fruit characteristics. Tongue River, Big Horn County. 

22 



Discussion and Conclusions 



Distribution and Abundance 

This study produced significant new information on 
the distribution and habitat characteristics of 
Astragalus barrii (Barr's milkvetch), Physaria 
didymocarpa var. lanata (woolly twinpod) and 
Lomatium nuttallii (Nuttall's desert-parsley) in 
southeastern Big Horn and southwestern Rosebud 
counties and in the state as a whole, since the 
latter two species are known to occur only in this 
area of Montana. A key question is whether, based 
on this information, we can reliably predict where 
these species might occur, or extrapolate their 
frequency and abundance across the landscapes in 
which they occur. 

Based on the habitat information we gathered, 
none of these species occupy landforms or 
vegetation types that are especially rare in this 
landscape. On the contrary, their habitats, while 
fairly distinctive, are quite common in the region; 
shale, clay siltstone, sandstone and red clinker 
characterize much of the study area. However, 
these species were often not present (or not 
found) in areas of apparently suitable habitat 
where we surveyed. This is underscored by the 
fact that we found them on only nine of our 25 
survey routes. Since most survey routes covered 
more than one potential habitat site, our actual 
success rate for finding these plants in apparently 
suitable habitat was even lower. This affirms that 
they are still uncommon to rare, and do not occur 
predictably and regularly in apparently suitable 
habitat. 

Our surveys primarily focused on large blocks of 
public land; other populations may well exist on 
smaller blocks of public land that were not sur- 
veyed. For example, the population of Nuttall's 
desert-parsley found in Rosebud County was on an 
isolated "" section of BLM land. Even in those 
larger BLM management units where we focused 
our work, surveys were by no means exhaustive, 
since the areas are large (measured in square 
miles) and the country is not easy to traverse. See 
maps in Appendix 2 for exact search routes.) It is 
therefore quite possible that additional populations 



exist even in the blocks where we conducted 
surveys. 

Finally, there is extensive private land in this region, 
and with very limited exceptions our surveys did 
not include private land. The public land that we 
surveyed was widely scattered, and travel between 
locations afforded the opportunity to visually assess 
miles of land that could be seen from the roads. 
Based on general habitat profiles and on-the- 
ground experience, casual observation identified 
significant potential habitat elsewhere throughout 
the area, most on unroaded private land with 
restricted access. It is reasonable to assume that 
some of these potential habitat sites support 
additional populations of the target species. 

Conservation and Management 

Few studies have considered factors that may 
affect the long-term viability of these species. 
Heidel & Marriott (1996) indicate that A. barrii is 
found on secondary range, and is characterized by 
a low, tufted growth form and early-season 
flowering. The species is, therefore, minimally 
affected by grazing management, unless livestock 
developments are placed near populations or 
unless grazing causes major shifts in plant 
communities that result in increased competition. 
Another indirect impact of grazing could be the 
introduction or increase of invasive species; both 
the exotic yellow sweetclover (Melilotus 
officinalis) and the native Venusis looking glass 
{Triodanis perfoliata) have been observed to 
dominate near some heavily grazed areas. It has 
also been suggested that herbicide or early-season 
pesticide spraying could potentially affect Barr's 
milkvetch (Heidel & Marriott 1996), or any other 
Species of Concern located close to weed 
treatment areas. 

Little information about regarding the ecology of 
woolly twinpod and Nuttall's desert-parsley exists. 
However, populations of both species were 
observed close to areas that were being grazed at 
the time of this study. Given the generally sparse 
vegetation associated with these species, their 



23 



habitat could be characterized as suboptimal range 
suggesting little or no threat from grazing. Woolly 
twinpod was also found on road cuts, which are 
often particularly vulnerable to erosion and weed 
invasions. 

Both woolly twinpod and Nuttall's desert-parsley 
sometimes occur on unstable habitats that may not 
be easily conserved on a site- specific basis, and 
may be better suited to a larger strategy based on 
compatible management. For example, one 
population of Nuttall's desert-parsley in Big Horn 
County was found in a stream channel, which 
would likely be subject to the scouring effects of 
runoff associated with a heavy rain. Further 
information on the ecology and distribution of these 
species will be needed to confidently propose long- 
term management strategies. 

Given that the landscape inhabited by these plants 
is relatively undeveloped and ecologically intact at 
present, the greatest potential negative impact to 
all three species would be extensive developments 
resulting in widespread conversion and/or 
fragmentation of native habitat and vegetation. In 
the past, surface coal mining has resulted in 
intensive though fairly localized impacts. 
Interestingly, woolly twinpod was first discovered 
in Montana in 1993 close to the Spring Creek Coal 
operation. This population was re-surveyed in 2001 
and still supports the largest population of woolly 
twinpod documented in Montana, as well as a very 
large population of Barr's milkvetch. 

Barr's milkvetch and, to some extent, woolly 
twinpod, tend to occupy high knobs and outcrops 
that are perhaps less likely to be selected as sites 
for mineral development. However they may still 
be vulnerable to secondary threats that result from 
extensive disruption of native vegetation, such as 
the introduction and spread of aggressive invasive 
weeds that reduce habitat quality and compete 
with native plant species. 

Related to weeds, we incidentally observed the 
exotic weed, Halogeton glomeratus (saltlover), 
at several locations during our field surveys in 
2002. This weed is known to be poisonous to 
livestock, with sheep being especially susceptible. 



It is well adapted to high salt levels, and leachates 
from its herbage will concentrate salts on the soil 
surface, further inhibiting competing plant growth 
(Young 2002). Increasing salinity of the soil could 
encourage spread of this species at the expense of 
native forage plants. 

Nuttall's desert-parsley grows on mid- to lower- 
slopes, especially along drainages-a habitat that 
could be more vulnerable to extractive 
development. All three known populations were 
found along, or closely bordering, drainages, 
implying a possible association with the availability 
of soil moisture that can be stored by the long 
taproots. Thus changes to the current hydrologic 
conditions may have the potential to impact these 
populations. However, there is still too little known 
about its distribution and ecology to make strong 
inferences about its conservation and 
management. 

In general, larger populations may stand a better 
chance of surviving some disturbance, with the 
many smaller populations perhaps being less 
resilient. It has also been suggested (Heidel and 
Marriott 1996) that larger populations of Barr's 
milkvetch appear to be buffered against drought 
conditions. 

Species Status Recommendations 

Woolly twinpod is now known from five locations 
in the state, and it is likely that more populations 
exist in Montana. One Montana population 
numbers over one thousand plants, however the 
other two are much smaller (ranging from 16-100 
individuals) and occupy small, localized habitats. 
This species has a rank of G5T2 SI, indicating its 
highly restricted distribution in Montana. The 
largest known population on BLM land is along 
Tidwell Creek and appears to be stable and 
productive. The Zook Creek population lies within 
a BLM Wilderness Study Area. Based on its 
global and state rank, this species warrants 
consideration for addition to the BLMis Sensitive 
or Watch list. 

Nuttall's desert-parsley has been recorded at three 
separate locations in the state, and is ranked G3 
S 1 , indicating its highly restricted distribution in 



24 



Montana. This species is presently on the BLM 
Watch list and is worthy of consideration for 
Sensitive status. The largest population is on a 
small BLM "" section surrounded by private land, 
and the other populations are either small or on 
private land. 

Barr's milkvetch is far more widespread, with 35 
occurrences currently documented in Montana, 
and a rank of G3 S2S3. Many occurrences, 
including several large populations, lie on BLM 
land and in the Custer National Forest (where it is 
designated USPS Sensitive and threats are 
probably low). Perhaps the largest population in 
the study area is adjacent to the Spring Creek 
Mine on private land. This population could be 
impacted by future expansion of mining activity. 
Another sizeable population lies on BLM land 
between Squirrel Creek and the South Pork Spring 
Creek. Two additional locations outside this study 
area, northeast of Birney, support large populations 
- the Kings Creek Well site on the Custer National 
Porest and the Gate Creek site, part of which lies 
on BLM land. 

Survey work over the past few years continues to 
document new populations of Barr's milkvetch. 
The number and widely scattered distribution 
pattern of populations makes this species 
somewhat less vulnerable to extirpation. It may at 
some point be considered secure enough for 
downgrading from special management status if 
more healthy populations continued to be 
discovered, and if most populations (including the 
larger ones) are verified to be stable, under 
compatible management and not at risk from 
current or impending land uses. However, at 
present, the current BLM designation of Watch 
seems appropriate. 



Recommendations for Future Work 

As noted previously, the fact that habitat for these 
three species is widespread in the study area 
indicates a high likelihood that additional 
populations remain undiscovered (Schassberger 
1990; Taylor 2001; Barton pers. obs.). BLM staff 
who conduct range assessments or other fieldwork 
within the study area are encouraged to become 
familiar with field recognition of A. barrii, P. 
didymocarpa var. lanata and L. nuttallii. 

A. barrii should be surveyed from early to mid- 
May when it is typically in full bloom. Dried 
remnant flowers often lose their color, making the 
species more difficult to confidently identify. Both 
P. didymocarpa var. lanata and L. nuttallii can 
be identified later in the year using vegetative and 
fruiting characteristics. 

With sufficient data (spatial coverages for soils, 
aspect, slope, vegetation cover, etc.), it would be 
possible to model and map potential habitat for 
these species across the landscape. Such an 
analysis could help better assess the extent of 
potential habitat and make tentative extrapolations 
about the speciesi possible abundance. It would 
also help focus any future surveys on areas with 
the best potential habitat. Pxpanding surveys to 
include private land, with landowner cooperation, 
would also help to better document speciesi 
distribution and abundance. Discovering and 
documenting additional populations can even, in 
some cases, provide evidence that a species is 
sufficiently common and/or compatible with 
current land uses to warrant downgrading or 
removal of special designation status. 



25 



References 

Bureau of Land Management (BLM). 1996. Special Status Species Plant Policy. Montana State Office, 
Department of the Interior. 49 pages. 

Carlson, J. C. and S. V. Cooper. 2003. Plant and Animal Resources and Ecological Condition of the Forks 
Ranch Unit of the Padlock Ranch, Big Horn County, Montana and Sheridan County, Wyoming. Unpub- 
lished report to The Nature Conservancy Montana Field Office. Montana Natural Heritage Program, 
Helena. 18 pp. plus appendices. 

Cronquist, A. et al. Intermountain Flora. Vascular Plants of the Intermountain West, U.S.A. Volume Three 
Part A. Hafner Publishing Co., New York and London. 1997. 446 pages. 

Dom, R. D. 1992. Vascular Plants of Wyoming, Second Edition. Mountain West Publishing, Cheyenne, 
Wyoming. 340 pages. 

Dom, R. D. 2001 . Vascular Plants of Wyoming, Third Edition. Mountain West Publishing, Cheyenne, Wyo- 
ming. 412 pages. 

Fertig, W. 2000. State Species Abstract: Physaria didymocarpa var. lanata. Wyoming Natural Diversity 
Database, Laramie, Wyoming. 2 pages. 

Heidel, B. L. and H. Marriott. 1996. Sensitive Plant Species Survey of the Ashland District, Custer National 
Forest, Powder River and Rosebud Counties, Montana. Unpublished report to the Custer National Forest. 
Montana Natural Heritage Program, Helena, Montana. 94 pages plus appendices. 

Heidel, B. L. and J. Vanderhorst. 1999. Sensitive Plant Species Surveys: Butte District, Beaverhead and 
Madison Counties, Montana. Report to the Bureau of Land Management, Billings. Montana Natural 
Heritage Program, Helena, Montana. 85 pages plus appendices. 

Schassberger, L. A. 1990. Report on the Conservation Status of Astragalus barrii, a Candidate Threatened 
Species. Unpublished report to the U.S. Fish & Wildlife Service, Denver. Montana Natural Heritage 
Program, Helena, Montana. 85 pages. 

Soil Survey of Rosebud County Area and Part of Big Horn County, Montana: Part I and Part II. 1996. United 
States Department of Agriculture, Natural Resources Conservation Service. In cooperation with Mon- 
tana Agricultural Experiment Station. 

Taylor, A. and R. Caners. 2001. Baseline Survey for Astragalus barrii Bameby (Barr's Milkvetch) and 
Physaria didymocarpa var. lanata A. Nels. (Woolly Twinpod) in Eastern Big Horn and Southwestern 
Rosebud Counties, Montana. Montana Natural Heritage Program, Helena, Montana. 27 pages. 

United States Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS). 2000. 
Montana Key for Ecological Sites. Unpublished Draft (10/2000) on file at the Montana Natural Heritage 
Program. 7 pages. 

Young, J. A. 2002. Halogeton Grazing Management: Historical Perspective. Journal of Range Management. 
55(3): 309-311. 

26 



Appendix 1. Global / State Rank Definitions 



Appendix 1. Global / State Rank Definitions 

HERITAGE PROGRAM RANKS 

The international network of Natural Heritage Programs employs a standardized ranking system to 
denote global (range-wide) and state status (NatureServere 2003). Species are assigned numeric ranks 
ranging from 1 (critically imperiled) to 5 (demonstrably secure), reflecting the relative degree to which 
they are "at-risk". Rank definitions are given below. A number of factors are considered in assigning 
ranks 6 the number, size and distribution of known "occurrences" or populations, population trends (if 
known), habitat sensitivity, and threat. Factors in a speciesilife history that make it especially vulnerable 
are also considered (e.g., dependence on a specific pollinator). 

RANK DEFINITIONS 

Gl S 1 Critically imperiled because of extreme rarity and/or other factors making it highly 

vulnerable to extinction. 

G2 S2 Imperiled because of rarity and/or other factors making it vulnerable to extinction. 

G3 S3 Vulnerable because of rarity or restricted range and/or other factors, even though it may 

be abundant at some of its locations. 

G4 S4 Apparently secure, though it may be quite rare in parts of its range, especially at the 

periphery. 

G5 S5 Demonstrably secure, though it may be quite rare in parts of its range, especially at the 

periphery. 

GU SU Possibly imperiled, but status uncertain; more information needed. 

GA SA Native in nearby states, but in Montana believed to be accidentally introduced, 

deliberately planted, or escaped from plantings. 

GH SH Historical, known only from records over 50 year ago; may be rediscovered. 

GX SX Believed to be extinct; historical records only. 

COMBINATION RANKS 

G#G# or S#S# Indicates a range of uncertainty about the rarity of the species. 

SUBRANKS 

T# Rank of a subspecies or variety; appended to the speciesi global rank of the full species, 

e.g. G4T3. 

QUALIFIERS 

Q Taxonomic questions or problems exist, more information needed; appended to the global 

rank, e.g. G3Q. 

? Denotes uncertainty or for numeric ranks, inexactness. 



Appendix 2. Maps of the Search Routes 



Appendix 2. Maps of the Search Routes 

Solid red lines indicate search routes. Astragalus barrii locations are marked by blue dots, Physaria 
didymocarpa var. lanata locations are marked by black dots and Lomatium nuttallii locations are 
marked by yellow dots. The large blue and yellow circles in Appendix 2. 1 represent occurrences with 
locational uncertainty based on information from collectors. 

The 1 :24,000 USGS Quad names associated with each map are as follows: 

Quad Name 



Appendix 2.1 



Appendix 2.2 



Appendix 2.3 



Decker 
Half Moon HiU 
Pearl School 
Toungue River Dam 

Holmes Ranch 
Lacey Gulch 
Pine Butte School 
Spring Gulch 

Forks Ranch 
Hamilton Draw 
Quietus 
Stroud Creek 



Appendix 2.4 



Bimey 
BimeySW 
Clubfoot Creek 
Spring Gulch 
Taintor Desert 
Toungue River Dam 



i& 



Appendix S.^ 



Mm 



AppetidlK 2 



£5:^ 



'« 



Append Ik 2.2 




Appendix 2. Overview of the four maps that follow known occurrences of Astragalus barrii, Physaria didymocarpa var. lanata and 
Lomatium nuttallii. 








V 


1 

1 






^'" ■■-•,- 






":: L ■"" ' 










Lugifid 



to-<iJ.^^":^'%'A*^j 



1 



iFiAlAi 



Vv^-^ 



v" 



l-'-l 






.■-? ■■^ 









Appendix 2. 1 Solid red lines indicate search routes. The large blue and yellow circles represent 
occurrences that have higher uncertainty as to exact location of the population. 











fS^^^ 




/ ) 


^JO .. 


■if"^^ "^"^ " 




■■ " [' ■" 


1- . 





■ 










V. 


if 




I 













Appendix 2.2 Solid red lines indicate search routes. 






■?-... 






^ v.. 



"■i 



^;?^:y. ■•%^-- ■ft..^^ .T.r^^=^?^>:;y^^^-s- " 
















^^^-^:a. 








lipA-r ■•■■ ' > 



* 



STj'^'nVt^ 












j^k:,'--! 



?^-T-^--:r 









Smrch rrxiiri N 



1 



iMile^ 



Appendix 2.3 Solid red lines indicate search routes. 




Appendix 2.4 Solid red lines indicate search routes.